Minimal Clinically Important Difference for the Jamar Hand Grip Dynamometer in CIDP: A Korea-UK Study

Area of Science:

• Neurology
• Clinical Measurement
• Biostatistics

Background:

• Grip strength (GS) is a key metric in chronic inflammatory demyelinating polyradiculoneuropathy (CIDP) assessment.
• Current guidelines suggest a 10% relative change as the minimal clinically important difference (MCID), often requiring averaged daily measurements.
• Optimal thresholds for detecting deterioration and for non-daily monitoring remain undefined.

Purpose of the Study:

• To establish precise MCID thresholds for grip strength changes in CIDP patients.
• To evaluate the accuracy of proposed absolute and relative GS change thresholds.
• To provide reliable monitoring guidelines for CIDP management.

Main Methods:

• Analysis of 350 GS assessments from 122 CIDP patients across two international centers.
• Classification of clinical changes (improvement, deterioration, stable) using patient perception and validated scales (INCA, ONLS, IRSD).
• Application of the Youden index to determine optimal MCID thresholds for absolute (kg) and relative (%) changes.

Main Results:

• The guideline-recommended 10% relative threshold demonstrated low specificity and accuracy.
• Derived thresholds of 5kg for improvement and 4.5kg for deterioration showed superior specificity and accuracy.
• A 20% relative change threshold also proved effective for detecting change in either direction.

Conclusions:

• Current 10% relative MCID for GS in CIDP is insufficient for reliable single-day assessments.
• Proposed thresholds (5kg improvement, 4.5kg deterioration, 20% relative) offer enhanced diagnostic specificity.
• These refined thresholds can improve the reliability of routine monitoring for CIDP patients.